Experimental results (e.g., Nawrot & Sekuler, 1990) and computational models (e.g., Wilson & Cowan, 1973) emphasize the dependence of excitatory and inhibitory interactions among detectors on the distance between them. We now report direct experimental tests of this distance-dependence. These experiments entailed the presentation of two pairs of visual elements, one pair constituting the context stimulus and the other the test stimulus. For collinear motions in the same direction, less luminance contrast was required to perceive motion for the test stimulus when there was motion for the context stimulus compared with when it was stationary. The context motion's excitatory effect on motion perception for the test stimulus decreased with distance. More surprising was the spatial anistropy of the facilitation effect. It only was obtained when the test stimulus was “in front of” the context stimulus; e.g., when the context motion was rightward, it facilitated the detection of rightward motion for test stimuli to the right of the context stimulus, but not to its left. For collinear motions in opposite directions, more luminance contrast was required to perceive motion for the test stimulus when there was motion for the context stimulus compared with when it was stationary. The context motion's inhibitory effect on motion for the test stimulus also declined with distance, but was not spatially anistropic.